Lipase-mediated preparation of optically active isomers of Rosaphen®

An alternative stereoselective synthesis of (R)‐ and (S)‐Rosaphen® via asymmetric catalytic hydrogenation

“…In the devised synthetic approach, the critical step is represented by the asymmetric hydrogenation of the ( E )‐2‐methyl‐5‐phenylpent‐2‐enoic acid 2 . The enantiomeric excesses obtained with the catalyst prepared by mixing [RuCl 2 (benzene)] 2 and ( R,S )‐Mandyphos‐4 or ( R,S )‐Mandyphos‐4 are excellent (99%) and comparable with the ones achieved by enzymatic approaches 10…”

“…Only very recently, while the present manuscript was in preparation, an enzymatic synthesis of the two enantiomers of Rosaphen has been published by Kawasaki et al, who also reported the description of their olfactive notes, albeit the relevant odor thresholds were not determined 10…”

Strepimidazoles A–G from the Plant Endophytic Streptomyces sp. PKU-EA00015 with Inhibitory Activities against a Plant Pathogenic Fungus

“…Compounds 2−5 were identified as analogues of 1 with different 4-acyl moieties, based on the comparison of 1 H and 13 C NMR data of 2a−5a to those of 1a (Tables 1−4) and the HRESIMS, COSY, HSQC, and HMBC correlations of 2a−5a (Figures 2 and S4). The absolute configuration at C-11 in 3 was tentatively assigned as S based on the comparison of its specific rotation ([α] 24 D +7.4) with those of phenylalkanes containing the same terminal 2-methylbutyl moieties ([α] 20 D +15.4 for S and [α] 24 D −13.0 for R). 23 Compounds 6 and 7 were identified as analogues of 1 with hydroxylated 4-acyl moieties, based on the comparison of 1 H and 13 C NMR data of 6a and 7a to those of 4a (Tables 1−4) and the HRESIMS, COSY, HSQC, and HMBC correlations of 6a and 7a (Figure 2).…”

Update 1 of: Enantioselective Enzymatic Desymmetrizations in Organic Synthesis

“…Both enantiomers of 1-amino-2,2-difluorocyclopropane-1-carboxylic acid have been synthesized in a preparative scale in high yields and ee's by means of analogue syntheses that make use of the desymmetrization of [1-(acetoxymethyl)-2,2-difluorocyclopropyl]methyl acetate (33) and the corresponding diol (35) by means of a lipase PS-catalyzed hydrolysis and transesterification, respectively (Scheme 8). 44 In an attempt to probe the mechanism by which glycosyltransferases recognize glycoproteins and assemble the core structures of O-linked oligosaccharides, two constrained glycopeptides were synthesized by means of a sequence in which The EED of 2,2-disubstituted propane-1,3-diols using wellknown acyl donors, i.e., vinyl and isopropenyl acetates, is a process that, although it has proven to be successful, usually suffers from low reactivity.…”